Integrative assessment of biomarker responses in Mytilus galloprovincialis exposed to seawater acidification and copper ions

Ocean acidification aggravates the toxicity of deltamethrin in Haliotis discus hannai: Insights from immune response, histopathology and physiological responses

Ocean acidification (OA) and other environmental factors can collectively affect marine organisms. Deltamethrin (DM), a type II pyrethroid insecticide, has been widely detected in coastal and estuarine areas, while little attention has been given to the combined effects of DM and OA. In this study, Haliotis discus hannai was exposed to three pH levels (8.1, 7.7 and 7.4) and three DM nominal concentrations (0 μg/L, 0.6 μg/L and 6 μg/L) for 14 and 28 days. The results indicated that experimental acidification and/or DM exposure led to impaired immune function and pathological damage. Additionally, acidified conditions and DM exposure induced oxidative stress, and gills are more sensitive than digestive glands. With increasing pCO2 and DM nominal concentrations, superoxide dismutase (SOD) activity decreased, whereas catalase (CAT) and glutathione S-transferase (GST) activities increased in the gills. Moreover, the expression levels of Toll-like receptor (TLR) pathway-related genes were upregulated after exposure. Integrated biomarker response (IBR) analysis proved that acidified conditions and/or DM detrimentally affected the overall fitness of H. discus hannai, and co-exposure to experimental acidification and DM was the most stressful condition. This study emphasizes the necessity of incorporating OA in future pollutant environmental assessments to better elucidate the risks of environmental disturbance.

Interactive effects of multiple antibiotic residues and ocean acidification on physiology and metabolome of the bay scallops Argopecten irradians irradians

Coastal areas are confronted with compounding threats arising from both climatic and non-climatic stressors. Antibiotic pollution and ocean acidification are two prevalently concurrent environmental stressors. Yet their interactive effects on marine biota have not been investigated adequately and the compound hazard remain obscure. In this study, bay scallops Argopecten irradians irradians were exposed to multiple antibiotics (sulfamethoxazole, tetracycline, oxytetracycline, norfloxacin, and erythromycin, each at a concentration of 1 μg/L) combined with/without acidic seawater (pH 7.6) for 35 days. The single and interactive effects of the two stressors on A. irradians irradians were determined from multidimensional bio-responses, including energetic physiological traits as well as the molecular underpinning (metabolome and expressions of key genes). Results showed that multiple antibiotics predominantly enhanced the process of DNA repair and replication via disturbing the purine metabolism pathway. This alternation is perhaps to cope with the DNA damage induced by oxidative stress. Ocean acidification mainly disrupted energy metabolism and ammonia metabolism of the scallops, as evidenced by the increased ammonia excretion rate, the decreased O:N ratio, and perturbations in amino acid metabolism pathways. Moreover, the antagonistic effects of multiple antibiotics and ocean acidification caused alternations in the relative abundance of neurotransmitter and gene expression of neurotransmitter receptors, which may lead to neurological disorders in scallops. Overall, the revealed alternations in physiological traits, metabolites and gene expressions provide insightful information for the health status of bivalves in a natural environmental condition under the climate change scenarios.

Intrinsic and extrinsic pathways of apoptosis induced by multiple antibiotics residues and ocean acidification in hemocytes of scallop Argopecten irradians irradians: An interactionist perspective

The increasing prevalence of antibiotics in seawater across global coastal areas, coupled with the ocean acidification induced by climate change, present a multifaceted challenge to marine ecosystems, particularly impacting the key physiological processes of marine organisms. Apoptosis is a critical adaptive response essential for maintaining cellular homeostasis and defending against environmental threats. In this study, bay scallops Argopecten irradians irradians were exposed to multiple antibiotics (sulfamethoxazole, tetracycline, oxytetracycline, norfloxacin, and erythromycin, each at a concentration of 1 μg/L) combined with/without acidic seawater (pH 7.6) for 35 days. The single and interactive effects of the two stressors on apoptosis and the underlying mechanisms in hemocytes of A. irradians irradians were determined through flow cytometry analysis, comet assay, oxidative stress biomarkers analysis, and transcriptome analysis. Results showed that apoptosis could be triggered by either AM exposure or OA exposure, but through different pathways. Exposure to AM leads to mitochondrial dysfunction and oxidative damage, which in turn triggers apoptosis via a series of cellular events in both intrinsic and extrinsic pathways. Conversely, while OA exposure similarly induced apoptosis, its effects are comparatively subdued and are predominantly mediated through the intrinsic pathway. Additionally, the synergistic effects of AM and OA exposure induced pronounced mitochondrial dysfunction and oxidative damages in the hemocytes of A. irradians irradians. Despite the evident cellular distress and the potential initiation of apoptotic pathways, the actual execution of apoptosis appears to be restrained, which might be attributed to an energy deficit within the hemocytes. Our findings underscore the constrained tolerance capacity of A. irradians irradians when faced with multiple environmental stressors, and shed light on the ecotoxicity of antibiotic pollution in the ocean under prospective climate change scenarios.

Ocean acidification induces tissue-specific interactions with copper toxicity on antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818)

Toxicity of contaminants in organisms under ocean acidification (OA) has attracted increasing attention in ecotoxicological studies. This study investigated how pCO₂-driven OA affected waterborne copper (Cu) toxicity in antioxidant defences in viscera and gills of Asiatic hard clam Meretrix petechialis (Lamarck, 1818). Clams were continuously exposed to Cu at ambient relevant (0/no metal exposure, 10 and 50 μg L^-1) and polluted-high (100 μg L^-1) concentrations in unacidified (pH 8.10) and acidified (pH 7.70/moderate OA and 7.30/extreme OA) seawater for 21 days. Following coexposure, metal bioaccumulation and responses of antioxidant defence-related biomarkers to OA and Cu coexposure were investigated. Results showed that metal bioaccumulation was positively correlated with waterborne metal concentrations but was not notably influenced by OA conditions. Both Cu and OA affected the antioxidant responses to environmental stress. Additionally, OA induced tissue-specific interactions with Cu on antioxidant defences, varying with exposure conditions. In unacidified seawater, antioxidant biomarkers were activated to defend against oxidative stress induced by Cu and prevented clams from lipid peroxidation (LPO or MDA), but failed to defend against DNA damage (8-OHdG). OA exacerbated Cu toxicity in antioxidant defences and increased LPO levels in tissues. Gills and viscera adopted adaptive antioxidant defence strategies to manage oxidative stress, with the former being more vulnerable to oxidative stress than the latter. MDA and 8-OHdG were sensitive to OA and Cu exposure, respectively, and were useful bioindicators for assessing oxidative stress. Integrated biomarker response (IBR) and PCA can reflect the integrative responses of antioxidant biomarkers to environmental stress and illuminate the contributions of specific biomarkers to antioxidant defence strategies. The findings provided insights for understanding antioxidant defences against metal toxicity in marine bivalves under OA scenarios, which is essential into managing wild populations.

Modeling integrated biomarker response (IBR) index for the mussel Mytilus galloprovincialis (Lamark 1819) exposed to heavy metal mixture using the CCF design

Marine pollutants such as heavy metals (HMs) are considered among the most copious oxidative stress (OS) inducers in marine organisms which leads to reactive oxygen species (ROS) formation. Complementary to our previous bioassays studies, the present research focuses on Catalase (CAT), Glutathione S-transferase (GST) and Malondialdehyde (MDA) as oxidative stress biomarkers and the integrated biomarker response (IBR) indexes (IBR₁ and IBR₂) as an ecotoxicological assessment tool in Mytilus galloprovincialis using central composite face centered (CCF) design. The oxidative stress biomarkers were measured in adult mussels (45-55 mm) on 3 days-exposed under different sub-lethal concentrations of cadmium (Cd), zinc (Zn), and copper (Cu). Using multiple regressions, ANOVA analysis revealed that experimental data fitted to second-order (quadratic) polynomial equations. The results showed that types, concentrations and metals combinations has a direct effect in CAT and GST activities, MDA level and IBR indexes. Additionally, metal-metal interactions were found synergistic (supra-additive), antagonistic (infra-additive) or zero interaction in the toxicological effect. As necessary, the optimization of the experimental results was done in order to determine the optimal conditions for the oxidative stress responses and IBR indexes. It was demonstrated that the CCF design combined with the multi-biomarker approach and IBR index can be used as an appropriate tool in ecotoxicological modulation and prediction of oxidative stress and antioxidant status by heavy metals in the mussels Mytilus galloprovincialis.

An Overview of Analytical Methods to Determine Pharmaceutical Active Compounds in Aquatic Organisms

There is increasing scientific evidence that some pharmaceuticals are present in the marine ecosystems at concentrations that may cause adverse effects on the organisms that inhabit them. At present, there is still very little scientific literature on the (bio)accumulation of these compounds in different species, let alone on the relationship between the presence of these compounds and the adverse effects they produce. However, attempts have been made to optimize and validate analytical methods for the determination of residues of pharmaceuticals in marine biota by studying the stages of sample treatment, sample clean-up and subsequent analysis. The proposed bibliographic review includes a summary of the most commonly techniques, and its analytical features, proposed to determine pharmaceutical compounds in aquatic organisms at different levels of the trophic chain in the last 10 years.